Gas turbine power plant for utilizing solid water-bearing fuel



May 4, 1954 Filed July 11 1949 C. H. SECORD GAS TURBINE POWER PLANT FOR UTILIZING SOLID WATER-BEARING FUEL 2 Sheets-Sheet 1 Wn-rsa E mu P547 v 2 7 sap/2x4 role Fig./

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. GAS TURBINE POWER PLANT FOR UTILIZING SOLID WATER-BEARING FUEL Filed July 11 1949 2 Sheets-Sheet 2 WM. BLW M A Home 3 Patented May 4, 1954 UNITED STATES GAS TURBINE POWER PLANT FOR UTILIZ- ING SOLID WATER-BEARING FUEL Campbell H. Secord, London,. England, assignor to Power Jets (Research and Development) Limited, London, England, a British company Application July 11, 1949, Serial No. 103,993

Claims priority, application Great Britain July 21, 1948 This invention relates to improvements in internal combustion gas turbines and has, as one of its objects, to provide a gas turbine engine which is of smaller dimensions for a given output, or which has a greater output for given dimensions than has hitherto been possible, thereby reducing the specific cost and weight of the prime mover accordingly.

Another object of the invention is to enable use to be made of a fuel which is wet in the sense that it contains or is otherwise combined with at least its own weight of water, but which may contain in the raw state or after preliminary treatment as much as ten or even more times its own weight, the maximum ratio depcndcharacter, making existing methods of drying very costly. The invention has particular reference to the use of peat.

The quantity of air used in a gas turbine is normally greatly in excess of the quantity required for complete combustion of the fuel since it is necessary to dilute the hot combustion gases so that a designed maximum temperature at the turbine inlet is maintained. By introducing water in the working fluid system and passing it through the turbine, the amount of excess air can be considerably reduced and the size of the plant correspondingly decreased, or alternatively the output increased without a corresponding increase in size of the plant.

Since the recondensation of exhaust steam which is mixed with the products of combustion would generally be prohibitively troublesome, the introduction of water into the working fluid system will entail the supply of very large quantities of water, i. e. of the order of that consumed by steam turbine station cooling towers. While enough water will usually be available for peakload and auxiliary applications, large scale baseload operation will in some localities only be possible if the fuel used itself supplies the water required. Accordingly, the invention provides a gas turbine plant wherein a wet fuel is consumed, part or all the water content thereof being introduced into the gas turbine cycle.

By way of example two forms of the invention are illustrated diagrammatically in the accompanying drawings.

7 Claims. (01. (so-39.05)

Figure 1 is a diagrammatic layout of a gas turbine power plant.

Figure 2 is a modification of the plant shown in Figure 1.

In Figure 1 there is shown a gas turbine driven alternator plant utilizing peat, comprising a centrifugal compressor I mounted on the same. shaft 2 as an axial flow turbine 3 which drives it. A power turbine 4 is mounted for series flow with turbine 3 and drives an alternator 5. The air delivery from the compressor I is led through a heat exchanger 5 to a fuel drier 1.

Raw peat to be used as fuel is excavated from its site I8 by a suitable grading machine or drag line (not shown) and is conveyed by a spiral conveyor 24 through duct I9 to a press 20 which serves to remove some or all of the mechanically bound water content of the peat. The press may take the form of a centrifuge or drum filter press. The method of winning the peat may be such as to secure the necessary amount of preliminary drying by drainage and natural evaporation.

The peat passes from the press 20 through duct 30 into the predrier ZI, in which it is subjected to a pre-drying process by the exhaust gases whereby some of the water content of the peat is evaporated (as will be explained more fully below). The peat with its remaining water content is then separated from the evaporated water and exhaust gases by separator 22, and led through duct 3| to peat pump 23 and then through duct 32 into the drier I, wherein some or all of the remaining water content is evaporated as will be explained below.

A pulverizer 8, situated at the outlet of the drier I, pulverizes the peat and breaks up the woody and fibrous particles. The peat is entrained in the air supplied to the drier I by the compressor I, and passed through passage 9 to combustion chamber I0. The coarser peat particles are separated off by means of a separator I I and re-circulated by passage I2 to the drier I.

The combustion chamber I0 is of a type providing as long a path as possible in order to ensure that practically all the peat has time to burn. Thus a suitable form is a cyclone or vortex type combustion chamber wherein the peat moves over a vortex path within a chamber having an axial outlet and performs a fairly large number of complete revolutions about the axis of the chamber while approaching the axial outlet through which the products of combustion pass to the turbine. One such combustion chamber is described in copending application Serial No. 250,701, filed October 10, 1951, in the name of Lloyd.

It is a characteristic property of peat that the ash produced by combustion thereof normally has a high fusion point and low abrasive propenties. For this reason, the ash may in some circumstances be. passed through the turbine without damage to the blades. However, in some cases, as for example Where the peat is contaminated with sand, it will be necessary to separate the coarser constituents of the 'iashffl'flm the combustion gases before they. enter-the turbine. Accordingly the products of combustion pass through the outlet passagetfi of .the combustion chamber into an ash separator 4.4,.the fly ash being taken off through duct l5.

Part of the combustion products passing'from the ash separator I4 are recirculated back through duct 16 into the drier I, while theremainder passes on through duct I? to drive the turbines 3 and 4.

The recirculated partof the gases mixes with the peat in the drier I and serves to evaporate some or all of the water content thereof as mentioned above. The. resulting steam is retained in the working fluid system and is expanded through the turbines together with-thecombustion gases resulting from combustion. of the fuel andexcess air.

The hot exhaust gases leaving the turbine 3 are ledinto the heat exchanger 6, in which part of theheat content.thereof is transferredto'the high pressureair from the compressor, and thence into the predrier 2 I. The hot gases mix with the incoming peat from the press 2% and evaporate part of the water content thereof. The peat with its remaining water content is separated off by separatorZZ as previously mentioned, while the exhaust gases and evaporated water are led into the spiral conveyor 24 to, preheat the incoming-peat by giving up part of their latent heat, and finally escape to atmosphere through vent 21,

The advantages of. reduction in size of the plant mentioned above can be realized to the greatest advantage by reducing the air-fuel ratio to the stoichometric value, i. e. the minimum value consistent with complete combustion of the fuel, and r then introducmgsufficient water into: the turbine to maintain the desired maximum turbine inlet .temperature. The introduction. of water under these conditions is herein termed maximum water injection. Itcan be shown that for gas turbine plant using maximum water injection, the overall sizeand'therefore the specific-cost andweight of the plantcan be reduced to approximately one third fora givenoutput or. con- -versely, for a givensize, the output. can'be increased approximately three fold, compared-with the corresponding normal dry cycle.

To achieve the above-mentioned advantages, 60 the incoming peat is dried in'predrier 2| to such an extent that its remaining water content when it is passed to the drier Lis substantially that conforming to a conditionof maximum water injection.

.The inlettemperature and output of the turbine maybe regulated by injecting va smallouantity of water into the duct I! through inlet 28.

In the modifiedplant-of Figure 2, the-peat, steam and recirculated combustion gases pass :from-the-drier 25 and pulverizenB-to ascparator -26 from which'the peat-and some of the gaseous .products pass into the combustion chamber H swhilethe most of these gaseous products bypass the combustion chamber by conduit 29 and are mixed with the combustion products in conduit I3.

I claim: 1. An open cycle gas turbine power plant for utilizing solid water-bearing fuel, comprising a fuel drier for evaporating at least part of the .Water content of the fuel having an inlet for said fuel and an outlet; a separator for separating at tleas tDart.ofasaidrevaporated water content from u; zthesolidicontentof the fuel having an inlet connected to the outlet of the drier, a first outlet for said'part of the. evaporated water content and a second outlet; fonsaid solid content; a combustion chamber having an inlet and an outlet, said inlet -45 being connected to the second outlet of the separator; meansfor supplying air to the combustion chamber; a turbine having an inlet connected to said outlet of the combustion chamber; and la vconnection by-passing the combustion 2o chamber, between the first outlet of the separator and the turbine inlet.

2. An .open cycle gas .turbine power plant utilizing solid water-bearing fuel, comprisinga fuel drier for evaporating at least part of the Water content of thefuel, having a first inlet .for

saidfuel, a second inlet and an outlet; a combustion. chamber having an inlet and an outlet, said inlet being connected to the outlet of the drier; means for supplying air to the combustion 3U chamber; a turbinehavinganjnlet connected to the .outlet of .the combustion chamber; and a connection between the outlet. of the combustion chamber and said second inlet of the drier to lead part. of the combustion gases into the drier 33 to evaporate said part. .of thewater content.

'3. An .open cycle gas turbine power plant utilizing solid water-bearingifuel, comprising a fuel drier for evaporating ,atleastpart of the .water content of the iueLhavinga, first inlet for 40 said fuel, asecond inlet and an outlet; a separator for separating -at least part of said evaporated water. contentfrom thesolid content of the fuel, having ,an inlet connectedto .the outlet ofthe vdrier, a first outlet, for said part .of the evaporated water content and a second ,outletfor said solid content; a combustion chamber having. an inlet andan outlet, said inlet being connected tosaid second ,outlet hi the se arator; .meansforsup- .plying air.to.the combustion chamber; a turbine having.an inlet connectedto .said outlet of'the combustion .chamber; .a .connection 'by-passing .the combustion chamber, between the. first. outlet .of the separator. and theturhine inlet; and a con .nectionbetween the outlet .of the combustion chamber and-saidsecond inlet ofthe drier to lead part of .the ,combustiongases into the drier ,to evaporate said part of the .water content.

4. An open cycle gas .turbine power plant for utilizingsol-id water-bearing fuel, comprising a .firstfuel .dr-ier. for .evaporatingpart of the water content orthe fuel, having an inletfor. said-fuel,

a first outlet ,to atmosphere for said evaporated part-of .the water content .and.a-second outlet :for thesolid content .and remaining water .con-

.tent of the .fuel; :a secondfuel drier forevap- ,orating at least partof the remaining .watercon- .tent having an inlet and an outlet, said inlet being connected .tosaid seconcltoutlet of the first drier; a combustionrehamber having an inlet and an out1et,' said inlet being connected .to the outlet of thersecondefueldrier means; for -.-supplying-.air

to. the combustion chamber;-.rand a turbine having an inlet connectedtothe outlet of the combustion --chamber.

15 5. 'Anopencyclegas turbine power plant utilizing solid water-bearing fuel, comprising a first fuel drier for evaporating part of the water content of the fuel, having an inlet for said fuel, a first outlet to atmosphere for said evaporated part of the water content and a second outlet for the solid content and remaining water content; a second fuel drier having a first inlet connected to the second outlet of the first drier, a second inlet, and an outlet; a combustion chamber having an inlet connected to the outlet of the second drier, and an outlet; means for supplying air to the combustion chamber; a connection between the combustion chamber outlet and the second inlet of the second drier affording a path for leading hot combustion gases into contact with the fuel in the second drier to evaporate at least part of the remaining water content of the fuel; and a turbine having an inlet connected to the combustion chamber outlet.

6. An open cycle gas turbine power plant utilizing solid Water-bearing fuel, comprising a first fuel drier for evaporating part of the Water content of the fuel having a first inlet for said fuel, a second inlet, and an outlet; a separator having an inlet connected to the outlet of the first drier, a outlet to atmosphere, and a second outlet for the solid content of the fuel and the remaining water content; a second fuel drier having a first inlet connected to the second outlet of the separator, a second inlet and an outlet; a combustion chamber having an inlet connected to the outlet of the second drier and an outlet; means for supplying air to the combustion chamber; a connection between the combustion chamber outlet and the second inlet of the second drier affording a path for leading hot combustion gases into contact with the fuel in the second drier to evaporate at least part of the remaining water content of the fuel; a turbine having an inlet connected to the combustion chamber outlet and an outlet connected to the second inlet of the first drier whereby hot exhaust gases are led into contact with the fuel in said drier to evaporate said part of the water content thereof.

'7. A method of operating an open cycle gas turbine power plant including a combustion chamber and a turbine, comprising the steps of supplying to the plant a solid water-bearing fuel, evaporating part of the water-content of the fuel and rejecting said part from the working fluid cycle, evaporating at least part of the remaining Water content, supplying the solid content of the fuel and any residual water content to the combustion chamber, supplying air to the combustion chamber in a quantity substantially corresponding to a stoichiometric air-fuel ratio, burning said solid content in said air, and supplying both the resulting combustion gases and said evaporated part of the remaining water content to drive the turbine, the quantity of water evaporated and rejected in said first stage of evaporation being such that the quantity of water remaining is substantially that required for a condition of maximum water injection.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 871,993 Goldsborough Nov. 26, 1907 1,197,456 Dinsmore Sept. 5, 1916 1,578,181 Balmer Mar. 23, 1926 1,809,819 Caller June 16, 1931 2,032,402 Colby Mar. 3, 1936 2,066,418 OM'ara Jan. 5, 1937 2,171,535 Berg Sept. 5, 1939 2,401,285 Woodward May 23, 1946 2,542,953 Williams Feb. 20, 1951 FOREIGN PATENTS Number Country Date 18,329 Great Britain Aug. 24, 1904 2,511 Great Britain Jan. 30, 1914 166,517 Great Britain Sept. 7, 1922 595,947 Great Britain Dec. 23, 1947 391,315 France Aug. 26, 1908 

2. AN OPEN CYCLE GAS TURBINE POWER PLANT UTILIZING SOLID WATER-BEARING FUEL, COMPRISING A FUEL DRIER FOR EVAPORATING AT LEAST PART OF THE WATER CONTENT OF THE FUEL, HAVING A FIRST INLET FOR SAID FUEL, A SECOND INLET AND AN OUTLET; A COMBUSTION CHAMBER HAVING AN INLET AND AN OUTLET, SAID INLET BEING CONNECTED TO THE OUTLET OF THE DRIER; MEANS FOR SUPPLYING AIR TO THE COMBUSTION CHAMBER; A TURBINE HAVING AN INLET CONNECTED TO THE OUTLET OF THE COMBUSTION CHAMBER; AND A CONNECTION BETWEEN THE OUTLET OF THE COMBUSTION CHAMBER AND SAID SECOND INLET OF THE DRIER TO LED PART OF THE COMBUSTION GASES INTO THE DRIER TO EVAPORATE SAID PART OF THE WATER CONTENT. 